A recent small subgroup of emergency department (ED) patients is responsible for a disproportionate amount of ED visits and costs. This subgroup, the heavy users of ED services, is identified as a medically and socially vulnerable population. The 'problem' of heavy ED use is nested within a complex of larger, interdependent problems including access to care, lack of primary/preventive services, absent or inadequate social services, and fragmented service delivery. Interventions aimed at reducing this subgroup's use of ED services have not proven effective, for reasons which remain unclear. The broad objective of this study is to contribute to improved understanding of the phenomenon of heavy ED use. The primary aims of the study are to: 1. Describe, in detail, the context in which heavy ED use occurs and explore the meanings of heavy ED use to patients who are heavy ED users. 2. Uncover and articulate the dimensions of the 'problem' of heavy ED users by examining it from several perspectives; and 3. Explicate the findings within a policy perspective, including implications for health care reform. The study is designed as an ethnography utilizing multiple data points and a two-level analytic structure. Data obtained from participant observation, patient and provider interviews, and medical records review will be analyzed using an interpretive approach of contrasting whole cases with one another and moving from whole to part, examining each for contrasts and similarities. Second-level analysis will link the findings to salient policy areas, identifying need criteria which will be examined for 'fit' with policy assumptions. The account of analytic findings is the doctoral dissertation. Such an account could usefully inform provider-and policy-level decisionmaking and provide a contextual ground for further research with this population. It is also anticipated that this in-depth, qualitative study will suggest avenues for future intervention studies.